The addition of phosphate groups to proteins are involved in phosphorylation, most commonly at a serine (S), Threonine (T), or Tyrosine (T) residue by a kinase, it is essential for pathway activation in cellular regulation, cell signaling, and cell growth.
It is the process of an addition of a phosphoryl group (PO3) to a molecule. It is critical for a cellular process, a large fraction of protein, sugars, lipids and other molecules are temporarily phosphorylated. The most abundant post-translational modification in eukaryotes is the protein phosphorylation.
In eukaryotic and prokaryotic organisms, an important regulatory mechanism occurs through the reversible phosphorylation of proteins. 230,000 phosphorylation sites exist in the human body, kinases phosphorylate proteins and phosphatases dephosphorylate proteins.
There are regulatory roles of phosphorylation:
- Biological thermodynamics of energy-requiring actions
- Mediates enzyme inhibition
- Important for protein-protein interaction through the recognition of domains
- Important in protein degradation
- Important in glycolysis― it helps in the transport, control, and efficiency
Types of Phosphorylation
Phosphorylation can occur on several amino acids within a protein. The formation of phosphoprotein results in the phosphorylation of amino acids and esterification reaction occurs when the phosphate group of the phosphoprotein reacts with the -OH group of serine, tyrosine, and threonine.
Phosphorylation of Histones
Eukaryotic DNA is organized with histone proteins in specific complexes, the chromatin. Facilitates the packaging, organization, and distribution of eukaryotic DNA are one of the chromatin functions. Histone phosphorylation has shown that it modifies the chromatin structure by changing protein to DNA or protein to protein interactions thus it has a negative impact on several fundamental biological processes, such as transcription, replication and DNA repair by the restriction of accessibility of a certain enzyme and protein.
Phosphorylation of Glucose
The phosphorylation of sugar is the first stage of catabolism, it allows cells to accumulate sugars since the phosphate group prevents the molecules from diffusing back across their transporter. It is an imperative process of the body to undergo glucose in the process of phosphorylation.
Detection and Characterization of Phosphorylation
To detect whether a protein is phosphorylated at a particular site, antibodies are used. Antibodies bind to and detect phosphorylation-induced conformational changes in the protein, these antibodies are called phospho-specific antibodies. Posttranslational modification isoforms can easily detect on 2D gels, the staining intensity has a relative amount of each isoform. Phosphorylation replaces neutral hydroxyl groups on serines, threonines, and tyrosines with negatively charged phosphates.